[citation needed] He then played for the New England Jr. Coyotes of the Eastern Junior Hockey League (EJHL) under legendary coach Gary Dineen.

[citation needed] After two seasons with the University of Michigan, Komisarek was selected seventh overall in the 2001 NHL Entry Draft by the Montreal Canadiens.

[citation needed] Komisarek scored his first NHL goal on March 20, 2006, against the Washington Capitals, where he was named the first star of the game.

[citation needed] In the 2006–07 season, Komisarek tied Mike Commodore of the Calgary Flames for most shorthanded goals scored by a defenseman with two.

[citation needed] On January 5, 2009, Komisarek played in the NHL All-Star Game, where he was named a starter as voted by the fans alongside his Canadiens defense partner, Andrei Markov.

[citation needed] In July 2009, Komisarek signed a five-year contract with the Toronto Maple Leafs worth an average of $4.5 million per season.

On January 2, 2010, Komisarek injured his shoulder in a game against the Calgary Flames, and on February 3, it was revealed that he would require season-ending surgery.

On March 21, 2013, he cleared waivers and with his permission was assigned to the Maple Leafs' American Hockey League (AHL) affiliate, the Toronto Marlies, for the remainder of the 2012–13 season.

His father, Roman Komisarek, was 24 when he moved to the United States, where he eventually opened an auto-body repair shop on Long Island.